[dxvk] Create dummy sampler and buffer on demand

We only need the dummy buffer for transform feedback, all other cases
are handled by null descriptors. May save a memory allocation.

src/dxvk/dxvk_unbound.cpp

@@ -3,8 +3,7 @@
 namespace dxvk {
   
   DxvkUnboundResources::DxvkUnboundResources(DxvkDevice* dev)
-  : m_sampler       (createSampler(dev)),
-    m_buffer        (createBuffer(dev)) {
+  : m_device(dev) {
 
   }
   
@@ -14,7 +13,47 @@ namespace dxvk {
   }
 
 
-  Rc<DxvkSampler> DxvkUnboundResources::createSampler(DxvkDevice* dev) {
+  VkBuffer DxvkUnboundResources::bufferHandle() {
+    VkBuffer buffer = m_bufferHandle.load();
+
+    if (likely(buffer != VK_NULL_HANDLE))
+      return buffer;
+
+    std::lock_guard lock(m_mutex);
+    buffer = m_bufferHandle.load();
+
+    if (buffer)
+      return buffer;
+
+    m_buffer = createBuffer();
+    buffer = m_buffer->getSliceHandle().handle;
+
+    m_bufferHandle.store(buffer, std::memory_order_release);
+    return buffer;
+  }
+
+
+  VkSampler DxvkUnboundResources::samplerHandle() {
+    VkSampler sampler = m_samplerHandle.load();
+
+    if (likely(sampler != VK_NULL_HANDLE))
+      return sampler;
+
+    std::lock_guard lock(m_mutex);
+    sampler = m_samplerHandle.load();
+
+    if (sampler)
+      return sampler;
+
+    m_sampler = createSampler();
+    sampler = m_sampler->handle();
+
+    m_samplerHandle.store(sampler, std::memory_order_release);
+    return sampler;
+  }
+
+
+  Rc<DxvkSampler> DxvkUnboundResources::createSampler() {
     DxvkSamplerCreateInfo info;
     info.minFilter      = VK_FILTER_LINEAR;
     info.magFilter      = VK_FILTER_LINEAR;
@@ -34,11 +73,11 @@ namespace dxvk {
     info.usePixelCoord  = VK_FALSE;
     info.nonSeamless    = VK_FALSE;
     
-    return dev->createSampler(info);
+    return m_device->createSampler(info);
   }
   
   
-  Rc<DxvkBuffer> DxvkUnboundResources::createBuffer(DxvkDevice* dev) {
+  Rc<DxvkBuffer> DxvkUnboundResources::createBuffer() {
     DxvkBufferCreateInfo info;
     info.size       = MaxUniformBufferSize;
     info.usage      = VK_BUFFER_USAGE_TRANSFER_DST_BIT
@@ -50,12 +89,12 @@ namespace dxvk {
                     | VK_BUFFER_USAGE_STORAGE_TEXEL_BUFFER_BIT
                     | VK_BUFFER_USAGE_TRANSFORM_FEEDBACK_BUFFER_BIT_EXT;
     info.stages     = VK_PIPELINE_STAGE_TRANSFER_BIT
-                    | dev->getShaderPipelineStages();
+                    | m_device->getShaderPipelineStages();
     info.access     = VK_ACCESS_UNIFORM_READ_BIT
                     | VK_ACCESS_SHADER_READ_BIT
                     | VK_ACCESS_SHADER_WRITE_BIT;
     
-    Rc<DxvkBuffer> buffer = dev->createBuffer(info,
+    Rc<DxvkBuffer> buffer = m_device->createBuffer(info,
       VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT |
       VK_MEMORY_PROPERTY_HOST_COHERENT_BIT |
       VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT);

src/dxvk/dxvk_unbound.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <mutex>
+
 #include "dxvk_buffer.h"
 #include "dxvk_image.h"
 #include "dxvk_sampler.h"
@@ -30,9 +32,7 @@ namespace dxvk {
      * and index buffers.
      * \returns Dummy buffer handle
      */
-    VkBuffer bufferHandle() const {
-      return m_buffer->getSliceHandle().handle;
-    }
+    VkBuffer bufferHandle();
     
     /**
      * \brief Dummy sampler descriptor
@@ -42,18 +42,22 @@ namespace dxvk {
      * still require different behaviour.
      * \returns Dummy sampler descriptor
      */
-    VkSampler samplerHandle() const {
-      return m_sampler->handle();
-    }
+    VkSampler samplerHandle();
     
   private:
     
-    Rc<DxvkSampler> m_sampler;
-    Rc<DxvkBuffer>  m_buffer;
+    DxvkDevice*             m_device;
 
-    Rc<DxvkSampler> createSampler(DxvkDevice* dev);
+    std::atomic<VkSampler>  m_samplerHandle = { VK_NULL_HANDLE };
+    std::atomic<VkBuffer>   m_bufferHandle  = { VK_NULL_HANDLE };
 
-    Rc<DxvkBuffer> createBuffer(DxvkDevice* dev);
+    std::mutex              m_mutex;
+    Rc<DxvkSampler>         m_sampler;
+    Rc<DxvkBuffer>          m_buffer;
+    
+    Rc<DxvkSampler> createSampler();
+    
+    Rc<DxvkBuffer> createBuffer();
     
   };